Color separation scanners are well known and are operative to scan two dimensional color images, such as prints or transparencies, and to produce electrical signals which represent color separations thereof for subsequent use in process color printing.
Conventional scanners, such as those manufactured and sold by Hell of Germany and Dainippon Screen Seizo of Japan, typically employ a rotating drum onto which the two dimensional color image is mounted. The drum rotates past a scanning head, which may comprise a CCD array, as taught in U.S. Pat. No. 4,256,969. According to that patent, a separate scan is carried out for each separation.
Various techniques are presently known for color separation in array detector based systems. One technique employs three primary Red, Green, and Blue filters installed over the scanning head of a single CCD linear or area array. A color image can be constructed by repeatedly scanning the image, each time with a different filter.
A second technique employs three colored fluorescent lamps. The image is repeatedly scanned, each time under the illumination of a different lamp.
A third technique employs three sensors and dichroic mirrors or filters for separating the three elements of color, each of which is detected by a separate sensor. In its current state of the art, this third technique has not achieved images of a high enough quality to fulfill the requirements of pre-press processing.
Another technique employs a single CCD chip including three linear arrays, each having deposited thereon a different color filter. Lines are read in three colors and combined using electronic hardware. A delay of several lines is interposed between the lines read in the different colors.
There is described and claimed in applicants'/assignee's copending U.S. Pat. No. 5,325,217, a scanner which comprises a movable support arranged for mounting thereon of a two-dimensional image to be scanned and color separation sensing apparatus arranged for sensing the two-dimensional image for providing electrical signals representing color separations of the two-dimensional image, the color separation sensing apparatus including a scanning head including a plurality of CCD arrays, each associated with a corresponding dichroic filter, operative for simultaneous scanning of the two-dimensional image.
That scanner comprises a movable support arranged for mounting thereon of a two-dimensional image to be scanned and having first and second ranges of operative orientations, television sensing apparatus arranged for sensing the two-dimensional image when the movable support is in a first range of operative orientations for providing a visible display of the two-dimensional image to an operator and color separation sensing apparatus arranged for sensing the two-dimensional image when the movable support is in a second range of operative orientations for providing electrical signals representing color separations of the two-dimensional image.
The scanner includes focusing apparatus arranged such that the color separation sensing apparatus and the television sensing apparatus are mounted on a common member, whereby focusing of the television sensed image automatically provides focusing of the color separation sensed image.